U.S. Pat. No. 4,830,399 (issued May 16, 1989) discloses a method for optimizing the operating characteristics of vehicles, especially of cars or trucks wherein the forces and/or moments acting on the vehicle or on parts thereof, respectively, are measured by devices integrated in elastic connections of the vehicle. The results of the measurements are processed and the operating characteristics of the vehicle are optimized on the results of the processing, for example, the suspension, attentuation and/or the clearance of the car body above ground is/are adjusted and regulated. The force measuring devices are integrated in the connecting joints of the spring supports of the vehicle between the shock absorber and the car body, the flanges of the force measuring device being fixed to the shock absorber and the car body with several screws.
The British laid open publication No. 81 10 972 (which serves as a priority document for British Patent Application No. 2097344 to Brearley) discloses a suspension with automatic level control for a vehicle, wherein a sensor is used to measure the level or height of the car body of the vehicle above ground. If the level differs from a reference value there are actuated two seperate hydraulic chambers provided at the suspension units to lift or lower the car body of the vehicle. This system requires extra special level sensors and separate hydraulic chambers in addition to the spring/shock absorber unit, thus raising the expense of this system.
The known so-called Lotus system does not use mechanical springs anymore but a hydraulic device as shock absorber and spring support of the car body. It uses a double-acting hydraulic cylinder fitted with a force measuring sensor and an extra level sensor and a level adjusting means controlled by a servo valve getting the information from a hybrid analog/digital computer. Furthermore, the suspension of each wheel requires an accelerating sensor, so that this construction with three sensors at each wheel is very complicated. Security makes it necessary to provide each wheel with a basic light spring to support the chassis in case of a motor deficiency or loss of pressure.